1. Field of the Invention
The invention relates to a hydraulic expansion chuck for clamping in a tool, in particular a drill or milling cutter.
2. Description of the Related
A chuck serves to connect a rotationally driven tool to the drive spindle of a machine tool. A chuck therefore has a pronounced chuck axis, about which the chuck and the tool which is clamped therein are rotated during operation. In the direction of this chuck axis, a chuck always has a tool-side end which is provided for receiving the tool and a machine-side end which is configured for connecting the chuck to the drive spindle of the machine tool. At the machine-side end, a chuck of this type as a rule carries a conical shaft, in particular a steep shaft, what is known as an HSC (hollow shaft cone) shaft or the like.
What are known as the hydraulic expansion chucks form a category known per se of chucks. In an expansion chuck of this type, the receptacle for the tool is formed by a thin-walled expansion bushing. The expansion bushing is surrounded by a pressure chamber which is filled with a pressure medium, for example an oil. The expansion bushing is configured in such a way that, if pressure is applied to the pressure medium, it is elastically deformed radially and in the process clamps in the inserted tool. A hydraulic expansion chuck has the advantage, in particular, that it damps jolts and vibrations which occur during operation. As a result, a particularly high surface quality and a long service life of the tool are achieved during machining.
WO 2005/097383 has disclosed a hydraulic expansion chuck of this type which can advantageously be used, in particular, in mold and die construction and has a long and narrow design which is required for this purpose. The known expansion chuck has a basic body which carries, at its tool-side end, the shaft which is provided for clamping the expansion chuck in the machine tool. An approximately bell-shaped clamping sleeve which is drawn out at the free end to form an elongate and narrow neck region is placed onto the basic body on the tool side. Here, a thin-walled and hollow-cylindrical projection of the basic body extends within the clamping sleeve as far as its free end, the pressure chamber being formed at this end between the projection of the basic body and the clamping sleeve. Here, the expansion bushing is formed in the inner region of the basic body, which inner region adjoins the pressure chamber. Here, a narrow annular gap which is concentric with respect to the chuck axis is formed between the outer circumference of the basic body and the clamping sleeve, which annular gap, as a pressure transfer channel, connects the pressure chamber to a pressure generation unit, the latter being accommodated in a widened, machine-side section of the clamping sleeve.
The known hydraulic expansion chuck is advantageous for producing very long, narrow chuck designs. However, the production of the expansion chuck is comparatively complicated. This relates, in particular, to the production of the thin-walled projection of the basic body and the pressure-tight soldering of the clamping sleeve to the basic body.
DE 100 07 074 A1 has disclosed a further expansion chuck. Said expansion chuck comprises a single piece basic body, on the machine-side end of which once again a shaft is formed, while the tool-side end of the basic body forms a clamping sleeve. Here, an inner sleeve which is separate from the basic body, and therefore also from the clamping sleeve, is inserted into the clamping sleeve, which inner sleeve contains an expansion bushing and delimits, on the inner side, a pressure chamber which surrounds it. At its tool-side end, the inner sleeve is provided with an outwardly protruding annular collar which overlaps with the clamping sleeve. Here, the annular collar extends over part of the radial width of the clamping sleeve which surrounds the annular collar on the outside. The interface which is formed between the annular collar and the clamping sleeve otherwise opens into the tool-side end face of the expansion chuck.